1. Field of the Invention
The present invention relates to a technical field of a reproduction controller for reproducing sound such as music when a mobile unit such as an automobile is driven.
2. Description of the Related Art
In recent years, a driving state detector has been developed which detects degradation in a driving mental state of a driver, that is, sleepiness, fatigue, fret, and so on during driving of a vehicle and notifies the driver of the degradation to encourage safe driving.
Meanwhile, kinds of methods have been studied to prevent an operator from dozing off in a long tedious operation. Recently, devices have been developed mainly for removing a cause of sleepiness, that is, environments suitable for a long tedious operation.
As a representative awakening holding device for preventing dozing by providing such agreeable and comfortable working environments, an awakening holding device described in Japanese Patent Laid-Open No. 8-196637 has been known which reproduces sound at fixed intervals or random intervals according to a circadian rhythm.
The circadian rhythm is considered to appear in an awakening reducing state where balance is lost between an accelerator system for activating brain stem reticular formation from sensory nerves or hypothalamus (autonomic nervous system) and increasing an awakening degree of cerebral cortex and a brake system for reducing an awakening degree by nuclei raphes. In order to hold awakening, it is desirable to change the balancing state into a state where the accelerator system has dominates to control a circadian rhythm phenomenon.
The awakening holding device of the above gazette has a sound source which generates sound for stimulating senses of a person and a measuring section for measuring a circadian rhythm, and the awakening holding device controls reproduction of the sound source so as to change the characteristics of a sound at fixed intervals or random intervals according to a measured circadian rhythm. For example, sound is intermittently reproduced according to the circadian rhythm by installing the awakening holding device in a mobile unit such as a vehicle, and dozing driving can be prevented by stimulating senses of a person.
However, with the above awakening holding device, it is not possible to listen to music selected by the user or music attracting interest of the user.
Particularly, since predetermined music of a reproduced sound source is processed, listening to the sound becomes boring.